This study is an interview-based grounded theory investigation that explores the phenomenon of the changes in L2 motivation over time and across contexts. Two Taiwanese international students who studied at a higher educational institution in the U.S. were interviewed about their motivational orientations prior to and after the study abroad transition and about how their study abroad experience over one academic year subsequently shaped their L2 motivation. Data analysis of the two participants’ self appraisal of their L2 motivational changes indicated that the study abroad transition had a great impact on the development of the participants’ L2 motivational self system (Dörnyei, 2005, 2009). The participants’ L2 goals, attitudes toward the English-speaking community, and self concept changed as a result of their study abroad experience. Several interacting internal and external factors shaped and reshaped the changes in their L2 self images, and these changes varied intra-person and across individuals, depending upon the individual learner’s self-determination and action control associated with specific contextual challenges. Furthermore, the changes in the participants’ ideal L2 self as a competent English user appeared to be temporary, and long-term stability of the ideal self images was observed.